This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Lipopolysaccharide (LPS) is a major component of the Gram-negative bacterial cell wall. LPS is comprised of three components: lipid A, core polysaccharide (Kdo and one or more heptose residues), and polysaccharide side chains. LPS biosynthesis that is halted prior to heptose addition results in a deep-rough phenotype and membrane permeability to antibiotics is increased. For this reason, the heptose biosynthetic pathway has been marked as a potential drug target. Our goal is to determine the mechanism of GmhA, an isomerase that catalyzes the first committed step of ADP-L-glycero-[unreadable]?-manno-heptose biosynthesis as well as GmhB and HldE which are also key players in LPS biosynthesis. Determination of the enzymatic mechanisms used by these proteins will aid in the rational design of inhibitors of GmhA, GmhB and HldE as a means to combat Gram negative infection.